12
Feb
Report Describes Complex Cumulative Risk Assessment Proposal to Implement California Law
(Beyond Pesticides, February 12, 2026) Editor’s Note. This is a piece about improving risk assessments and a proposal that could offer a more realistic characterization of the harm associated with the complexities of pesticide exposure. Beyond Pesticides notes that risk assessment methodology, unless it is considered in the context of a rigorous alternatives assessment, begins with the mostly false assumption that petrochemical pesticides are needed (or are essential) to achieve cost-effective pest management, agricultural productivity and profitability, and quality of life, when, in fact, this is not the case. Therefore, improved risk calculations—as the article being reviewed here proposes—while important to characterizing the harm and the unknown adverse effects associated with pesticide use, still impose some level of harm deemed by the government to be acceptable. Even worse, the adverse effects of exposure cannot be fully characterized because of uncertainties or a lack of data on harmful endpoints, as is the case currently with endocrine-disrupting pesticides not fully evaluated by the U.S. Environmental Protection Agency (EPA), California’s Department of Pesticide Regulation (DPR), or other regulatory bodies. These pesticides are known to induce cancer, reproductive harm, infertility, biodiversity decline, and other life-threatening, often multigenerational, effects. The authors do recognize the serious challenges in developing an accurate assessment of risk, acknowledging that field mixtures of pesticides constitute countless variations that would need to be anticipated. And, they recognize that risk mitigation measures typically respond to risk assessments, but are not sufficient to achieve an “acceptable†risk. However, we emphasize that the basic standard in federal pesticide law, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), requires protection against “unreasonable adverse effects†to people and the environment, a standard that should not, but does currently, allow for hazards or uncertainties when less- or non-toxic alternatives are available. Even so-called health-based standards reliant on risk assessments, such as the tolerance setting process in the Federal Food, Drug, and Cosmetic Act (FFDCA), accept a level of harm and uncertainty despite the availability of practices and products that eliminate the identified risk. We urge better assessment of harm and full disclosure of what is not known so that clear-eyed decisions can be made to take meaningful precautionary steps to adopt alternative practices and products, now available, to tackle the existential health, biodiversity, and climate crises of our time.
A University of California, Los Angeles (UCLA) report, Building Capacity for Robust Pesticide Regulation: Part I – Cumulative Impacts, underscores some of the critical gaps in federal and state pesticide law and the opportunity for comprehensive reform to strengthen cumulative impact assessments for pesticide products. The main authors of this report—Timothy Malloy, JD, professor at UCLA School of Law, and Patrick Allard, PhD, professor at UCLA Institute for Society and Genetics— build on three previous reports (see here, here, and here) to assess these gaps and opportunities from regulatory, scientific, legal, policy, and environmental justice perspectives. The main goal for this specific report is to develop a toolbox of scientific methodologies/approaches for California’s Department of Pesticide Regulation (DPR) and the local permitting process by county agricultural commissioners (CACs) to engage in more comprehensive and cumulative impact assessments under their purview.
Even in a state like California, which has passed legislation requiring the assessment of cumulative impacts by DPR’s pesticide registration process and CAC’s local permitting system, implementation remains insufficient due to a lack of clear methods and guidance from the top down. The report calls for a paradigm shift from the whack-a-mole approach focusing on regulating individual pesticides to a cumulative risk framework, citing various cumulative risk assessment methodologies.
Public health and environmental advocates continue to call for a transition to organic land management practices that are consistent with the precautionary principle of no tolerance for pollution from synthetic and fossil-fuel-based agrichemicals, given the failure of risk assessment-based systems to adequately address the public health, biodiversity, and climate crises. In a regulatory and political environment riddled with industry influence, communities are seeking to protect themselves from toxic chemical exposure and the threats of biodiversity collapse and the climate crisis through the adoption of nature-forward pest management consistent with organic principles. (See here, here, and here for examples.)
Key Concepts from the Report
The authors first distinguish between some key concepts, including cumulative exposure, cumulative risk, cumulative impact, and pesticide mixtures. This is followed by the authors’ proposal for alternative methodologies, incorporating cumulative impact assessment of pesticide mixtures into regulatory review.
Cumulative exposure refers to the various pathways (e.g., soil, air, water) and routes (e.g., ingestion, dermal, inhalation) through which pesticide exposure occurs. Cumulative risk is the combined risk from multiple exposures, with cumulative impact stacking on additional dimensions (or “stressors,†as the report refers to them), including socio-economic status or heat stress, among others.
The report also describes three types of pesticide mixtures, some of which individuals or communities simultaneously face. These include the following:
- Product mixtures, where one registered pesticide product is a pre-mixed formulation of multiple active ingredients, “inert†ingredients, adjuvants, and other substances. For example, the new (as of 2024) Roundup Weed and Grass Killer “Exclusive Formula” consists of triclopyr, fluazifop, and diquat—three different active ingredients registered with the U.S. Environmental Protection Agency (EPA) within one product.
- Field mixtures, where multiple pesticide products are added to a tank and simultaneously sprayed on crops—either because the EPA-registered label is “silent with respect to mixing, leaving the decision to the grower or applicator†or “the application instructions on the product label require or encourage mixing with other pesticides or with materials such as emulsifiers or wetting agents.â€
- Coincidental mixtures, when separate applications from individual pesticide products and field mixtures from adjacent fields form into new combinations that could lead to additive (synergistic) or subtractive effects.
Legal and Regulatory History
California’s pesticide regulatory regime is a two-tiered system—DPR at the state level registering pesticide products and CACs at the county level permitting their use. As stated in the report,
“With very limited exceptions described below, DPR does not evaluate the impacts of any of the three cumulative exposure scenarios. DPR guidance and website statements do not discuss the agency’s approach to cumulative exposures. Indeed, in evaluating the DPR’s risk assessment process, the National Research Council concluded in 2015 that ‘[t]he extent to which DPR has considered such cumulative risk assessments is unclear.’â€
The most significant legal development in recent memory was a state court decision (PANNA v. DPR 2017) that clarified the scope of state regulatory agencies engaged in risk assessment for pesticides in the context of California Environmental Quality Act (CEQA)’s mandate for evaluating cumulative environmental impacts for agency decision making.
Before this case, it was unclear whether DPR’s pesticide registration regulatory process was subject to CEQA; the court’s decision clarified that DPR must analyze cumulative effects for new pesticide active ingredients, and CACs cannot ignore cumulative impacts in their local permitting decision-making. While federal pesticide registration law governed by FIFRA does not require cumulative impact assessment, under the federal tolerance setting process, EPA is required to conduct a cumulative risk assessment for food use pesticides that have a “common mechanism of toxicity.†The governing law for the setting of food tolerances, FFDCA [Section 408(b)(2)(D)(v)—21 U.S.C. 346a(b)(2)(D)(v)], requires that the cumulative analysis for food use pesticides includes non-dietary exposure. (See EPA guidance.)
Cumulative Impact Assessments for Pesticide Mixtures
There are several cross-cutting principles that created the foundation for the report’s main recommendations:
- Understand the strengths and weaknesses of the regulatory bodies in question; for example, DPR has more scientific and regulatory capacity, CACs have local knowledge but limited staff with scientific expertise, and the state’s scientific health agency (Office of Environmental Health Hazard Assessment, or OEHHA) has expertise in environmental risk assessment more broadly and data analysis;
- Take inventory and use existing data and resources, as mentioned in the above point about the strengths and weaknesses of various regulatory bodies in the state;
- New registration and risk assessment models must be efficient and targeted to avoid regulatory or industry burden; and,
- Long-term funding from the California legislature is necessary.
Given the failure to abide by legal requirements and constraints under the current scientific risk assessment process for cumulative assessment of field or coincidental mixtures, the report calls for four new common features of cumulative impact assessments, including:
- The creation of new cumulative assessment groups (CAGs) based on potential shared health outcomes, including a trigger measure for regulatory action based on the findings that multiple pesticides cause a common toxic effect(s) on an organ, organ system, or “act through a common mechanism of action at the molecular level.†The authors cite this approach as a way to clear up vagueness from a regulatory perspective and ensure regulatory compliance is cost-effective by taking action at strategic times;
- The development of a tiered assessment and default assumptions for regulatory bodies. For example, each approach in the tiered system would start with default assumptions based on what is already known about the chemicals;
- Utilize existing data sets and tools, such as California’s Pesticide Use Reporting (PUR) database, CalEnviroScreen community scores, epidemiological studies, and DPR’s air monitoring programs, to ensure that regulatory decisions are evidence-based while also emphasizing a proactive approach; and,
- Integrate CalEnviroScreen (a state-level cumulative impact tool similar to EPA’s former Environmental Justice screening tool) to inform registration and permitting decisions for DPR and CACs, respectively. DPR could leverage CalEnviroScreen to observe if a disproportionately impacted community will face additional burdens, and CACs can utilize some geographical tool to mandate enhanced protections like no-spray zones or prohibit additional permits based on existing pollution burdens.
In terms of the various pesticide mixtures, the report offers different recommendations based on product mixtures, field mixtures, and coincidental mixtures.
For product mixtures that contain multiple active ingredients and/or other components, the authors recommend whole product assessments, component-based assessments, or a hybrid assessment that combines elements of both. Whole product assessment could be significant in that, for any new registered product, DPR could require chronic toxicity studies before approving its use; component-based assessment is fairly similar to the status quo, although the authors point out that manipulating the hazard index or relative potency factor methods could help inform cumulative risk once combined. The authors mention a handful of hybrid assessment models, including one in which DPR could require a specialized test for a product with two ingredients that may impact the same organ (e.g., liver) to see if the combination is synergistic. (For more details on this section, see pages 25 to 29 of the report.)
Field mixtures are tougher to regulate since there are countless variations that may be challenging for regulators to anticipate; however, DPR could identify the most prevalent or concerning combinations of products to require testing before their use can be permitted by CACs at the county level. A more precautionary approach is a component-based/additive model where DPR assumes that any field mixture could have an additive effect and uses a hazard index calculation to assess which cumulative exposures meet the sum risk threshold. The report ultimately recommends a hybrid assessment process where DPR considers cumulative risks of intentional mixtures and decides not to approve a label encouraging a tank mixture or explicitly state which other active ingredients are allowed or prohibited from being mixed. DPR would take more of a leadership role for CACs in that they would develop a standardized approach for CACs to assess new tank mixtures. (For more details on this section, please see pages 30 and 31 of the report.)
The report recommends a combination of two approaches for coincidental mixtures, beginning with the interim use of qualitative tools that would lead to an extended component-based assessment. DPR and California’s Office of Health Hazard Assessment (OEHHA) would collaborate to develop a cumulative risk assessment screening tool that “relies upon existing component based risk assessment methods and well-established exposure models†and “draws upon the expertise and resources of DPR and OEHHA while enabling the CAC staff to better exercise their mandate to consider local conditions in restricted material permitting.†As this tool is being developed and implemented, CACs would utilize a qualitative cumulative risk assessment tool rooted in the concept of control banding that industrial hygienists employ when there are limited data and resources available. (For more details on this section, please see pages 31 to 36 of the report.)
Risk Management
The authors recognize that risk calculations are considered in regulatory decision-making as part of a risk management decision that seeks to mitigate risks to an “acceptable†level. While pointing to the likely risk mitigation measures that may reduce hazards, they suggest that safer alternatives may be among the measures considered.
The authors state: “The goal of risk management is to identify a set of options that can reduce hazard and exposure. It also aims to evaluate those options to determine if they provide acceptable protection of human health and the environment. Risk management often presents trade-offs that complicate decision-making. Effective risk management must craft a combination of mitigation measures that reduce hazard and exposure to acceptable levels, are enforceable in the field, allow for effective pest management, and do not result in other unacceptable health or environmental impacts. Mitigation measures can include, among other things, controls on timing and frequency of application; limits on crops to be treated; use of feasible, safer alternatives; use of personal protective equipment by workers; and required buffer zones to protect people or wildlife near the application site. If mitigation measures cannot reduce the risk to acceptable levels, DPR can deny registration of the pesticide product. Mitigation measures may be implemented through regulations, permit conditions, or labels (in conjunction with the United States EPA).â€
Call to Action
You can take action today by asking your mayor to adopt a policy and program for organic management of your community’s parks and public spaces.
Additionally, you can sign up for Action of the Week and Weekly News Update to stay notified on ways you can take action to expand public investments and programs that expand organic land management, in agricultural contexts and on public green spaces, parks, and playing fields, to move beyond a reliance on synthetic materials.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Building Capacity for Robust Pesticide Regulation: Part I – Cumulative Impacts
